Susan Houde-Walter was elected for a three-year term as vice president of the Optical Society of America at its annual meeting held last week in Orlando, Fla. Ursula J. Gibson, James R. Leger and Alexander A. Sawchuk were named new directors at large, also for three years. Houde-Walter will be inducted on Jan. 2.   . . .   Derek Houghton was appointed director of sales and marketing, silicon technology, at AIXTRON Inc.